Dark matter annihilation with s-channel internal Higgsstrahlung

TL;DR

This paper explores how s-channel internal Higgsstrahlung can enhance fermionic dark matter annihilation, reducing chirality suppression and potentially dominating over other processes, with implications for indirect detection and collider searches.

Contribution

It demonstrates that s-channel internal Higgsstrahlung can alleviate chirality suppression in dark matter annihilation and dominate even for Dirac dark matter, unlike t-channel processes.

Findings

S-channel Higgsstrahlung reduces chirality suppression in dark matter annihilation.

The spectral shape of cosmic rays is similar to t-channel Higgsstrahlung for heavy mediators.

S-channel Higgsstrahlung can dominate the annihilation process even for Dirac dark matter.

Abstract

We study the scenario of fermionic dark matter that annihilates to standard model fermions through an s-channel axial vector mediator. We point out that the well-known chirality suppression of the annihilation cross section can be alleviated by s-channel internal Higgsstrahlung. The shapes of the cosmic ray spectra are identical to that of t-channel internal Higgsstrahlung in the limit of a heavy mediating particle. Unlike the general case of t-channel bremsstrahlung, s-channel Higgsstrahlung can be the dominant annihilation process even for Dirac dark matter. Since the s-channel mediator can be a standard model singlet, collider searches for the mediator are easily circumvented.